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PMDG J41 Stop Latches
48 replies to this topic
Posted 02 September 2009 - 10:50 AM
With the JS4100 coming soon, I wanted to take a couple of minutes and prepare you for one of the lessons you will learn.The geared turboprop may be new to some of you, it has been for me. I want to give you a heads up about something called STOP LOCKS. These are mechanical latches on the props that hold the blade in flat pitch and they are required because: 1) Loss of oil pressure in the prop dome causes the blades to feather (this means they align with the airflow and present minimum drag desired if engine is out). 2) The electric starter/generator does not have enough power to spin feathered blades up to speed for start, the blades have to be in flat pitch.The reason this is important is because if you try to start when not in the stop locks, then it will simply crank until the starter shaft overheats and it will shear.The gotchya' is when you shut down and look at the props, gee! They look like they are on the stop locks, but walk away from the plane and in about a minute or so after the oil pressure bleeds off in the prop domes the blades will feather with or without you watching.The shutdown procedure includes pulling the power levers into reverse AFTER the RPM has decreased below 50%.If this isn't done right, you will end up with feathered props and you will have to either spend an extra few minutes running a special little oil pump that slooowly unfeathers the props before you start or you unawaringly try to start with feathered props and as I mentioned, that is not good.Here is a picture of feathered props (Not STOP LOCK):[attachment=8819:NOTSTOPLOCK.jpg]Compare it to the flat pitch blades on the STOP LOCKS:[attachment=8820:STOPLOCK.jpg]I hope this thread is not referenced too many times, but I am sure it will come up.
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Posted 02 September 2009 - 12:54 PM
Hi Dan. Just wondering something. On Garretts there is a cannister that get pressurized after you get the engine going. On shutdown, for Garretts, if someone has ever heard this, you will hear a garrett speed up for a second or two on shutdown and then it will continue to shutdown. What this is is the cannister releasing the built up pressure to clear out the engine from fuel. If fuel is left uncleared, what happens is there will be residual fuel left on the fuel "injectors" and with the amount of heat in the engine will coke the fuel to the fuel nozzles and reduce the effectiveness of the nozzles which will require replacing. I am sure everyone has seen pilots get out and spin the props after shutdown. Some people think it is to cool the crankshaft properly but this is not true. It is to blow air through the nozzles so it can blow off any remaining fuel that is left on the nozzles. If I remember correctly this is "supposed" to be done within 2 mins of shutdown. Not sure where that theory of the crankshaft derived from but the crank shaft is too short and would not bend due to uneven cooling. Its like trying to bend a piece of 1 inch think plywood that is 2 inches long. You can't. Anyways I was wondering if the quick spool-up on engine shutdown was simulated Dan. thxJack
Posted 02 September 2009 - 01:02 PM
Jack,You're referring to the Air Purge system, and on the TPE331, it happens automatically when the STOP buttons are pressed. You can hear the RPM increase momentarily, and the EIS will show a momentary increase in both RPM and EGT.The Air Purge system only works if the accumulators are charged, which requires that the engine be operated at greater than 95% RPM for a minimum of 5 seconds.The PMDG J41 simulates this perfectly.Nick
Posted 02 September 2009 - 01:53 PM
John,This will happen any time you have to start/stop the engines - yes the default is to start up with the engines running, but you can make a save flight that has whatever configuration you want. A lot of people like to go through the startup procedure and will likely use a "short turn" or "long turn" saved flight that has the aircraft in the condition a pilot would most likely find it in when starting a leg...
I thought fsx started the sim with the engines running!!! Or is this if you do a continuation flight?I bet I'll forget anyway lol. That's a super livery in the background by the way.John Ellison
Posted 02 September 2009 - 02:17 PM
I don't know what the O key does, but it sounds like it's the same as what Dan mentioned about the oil pump (Unfeather) switch. Very simple to use, but if you don't start the engine quickly enough (I think you get a minute or so), the props will feather again. If you're anything like me you will end up using that switch more than you would like to.
Please tell me that if you forget you have to hand crank the oil pump by pressing O repeatedly on your keyboard until they are back into position (yes I'm kidding)
Posted 02 September 2009 - 02:36 PM
Robin, I echo your feelings QUADRUPLED, and Ryan......, I CAN HARDLY WAIT !!!! Note: Please pardon the shouting, but I'm very excited, because the J 41 seems to be about to take us even closer to, "As Real As It Gets" on a PC, and I am very impulsive I may have to stop eating for a while and get me a new, top notch PC to really do this aircraft and myself justice. Please,....Pretty Please let it be released tonight, I CAN'T BEAR IT ANY LONGER !!! There I am, shouting again !!AHH Well, better get back to flying my MD-11 Best Regards,GodfreyG
Posted 02 September 2009 - 02:43 PM
BRILLIANT!!! Looking like this J41 is a fantastic tribute to the programmers and pmdg I'll be rubbing my hands with glee (not available in the shops) same as I was when with the Aerosoft Catalina startup - truly brilliant, foul the plugs and you've had it lol.And yes Ryan, I do like to start in cold&dark, adds to the whole experience John Ellison
Posted 02 September 2009 - 03:06 PM
Thank you Dan for taking the time to explain this.Really looking forward to this plane. Very impressed with what you folks have done, and I have not yet really seen all...Looking forward to reading the manuals and really looking forward to the maiden flight (for me) to the Aleutians.No, I am not excited at all.
Posted 02 September 2009 - 03:45 PM
Thanks for asking. I lived and served out there for several years and have many wonderful memories. Plus, the weather is crap most of the time, which makes for some...well...fun times.Scary times for some.I live on the mainland now.
Chad, may I ask you why that destination? Is it a real life destination or is it just where you live...?
Posted 02 September 2009 - 03:58 PM
Well, I hear ya Pieter. Not for everyone on an initial flight I guess. I love flying up here for real and virtually. This "kid" has lived up here (Alaska) all my life, flown out there many times and don't think about it really, other than being aware of some of the potential hazards.If you want a bit of a challenge, fly in to Dutch. That'll make ya pucker a wee bit.Cold Bay has about a 14 thousand some odd foot runway (US space shuttle alternate landing) and Adak has a large runway also. Much easier to manage.I am flying (maiden) from PANC (Anchorage) to PACD (Cold Bay) then PADU (Dutch Harbor/Unalaska). Back (in direction) to PASD (Sand Point) then PAKN (King Salmon). Back to PANC.I am itching to get this show on the road.
Posted 02 September 2009 - 04:10 PM
Well, last thing about this because it's completely off topic, but coming from The Netherlands I was triggered by the name Dutch Harbor. Wikipedia: "Dutch Harbor was so named by the Russians because they believed that a Dutch vessel was the first European ship to enter the harbor." Funny connection. As a patriottic Dutch man I will fly to that airport for sure
Posted 02 September 2009 - 04:33 PM
Have you guys tried firing up FSX like this: Select"Free flight" and departure field and time using the default Trike or Cessna. Then you shut the default aircraft down completely, battery, mags, avionics, fuel cutoff. Then select the J41.Would that too make it "cold and dark"? That seems to work for most advanced addons.And the pictures are great! That looks like some kind of prototype paint. Very cool.